A study was undertaken to determine whether the Bio-Rad Hba1 test could be used to replace the method previously used to determine glycosylated hemoglobin concentration (modifications of Gabbay and of Trivelli). Blood samples were taken from 22 normal male, 24 normal female, 11 diabetic male, and 22 diabetic female Pima Indians who were participating in epidemiological studies of diabetes on the Gila River Indian Reservation in Arizona. Both methods shown increased HbA1 concentrations in the diabetic groups when compared to the normals, but the kit values were lower, in general, than the values obtained with the previously used method. One set of control samples used revealed a need to run all assays at a constant temperature and to establish a series of frozen controls prior to beginning long-term epidemiological studies.